The roller pump, used to pump blood flow during cardiopulmonary bypass and long term circulatory support, is a constant blood flow device. It maintains constant flow independent of the clinically expected changes in inlet pressures. A decrease in blood supply to the inlet of the pump without a concomitment decrease in pump speed can cause excessive suction leading to air embolism, thrombosis and damage by the "venous" cannula to the vessels's intima or, with a bubble oxygentator, the emptying of the oxygenator and pumping air to the patient. Present safety features are either ON-OFF controls, or it cannot be used without modifying the standard roller pump. It is the purpose of this research to design, fabricate and evaluate a new innovative disposable pump chamber for the standard roller pump that self-controls the pump flow as a function of inlet or filling pressure, much like the natural heart. The pump chamber consists of an easily collapsible thin wall tubing (TWT) housed and sealed in a standard pump tubing. The inner TWT serves to pump blood and the outer tubing serves as a mechanical support and controlled pressure environment for the TWT. This pump chamber can provide additional safety during open heart surgery and a very inexpensive self-controlling mechanism for long term circulatory support.